The mechanistic aspects of a novel methodology for the electrochemical hydride generation (EcHG) of cadmium, entitled as the catholyte variation, have been studied. The hydrogen overvoltage of different cathode materials was determined in dilute electrolyte. The lead-tin alloy used as the cathode material for the EcHG of Cd had the highest hydrogen overpotential. In this technique, both electrolyte medium and cathode surface would change during electrolysis. The catholyte variation EcHG coupled with a flame heated quartz tube atomizer (QTA) atomic absorption spectrometer (AAS) produced peak-shaped transient signal of Cd. The analytical signal was significantly enhanced at neutralization time. The simultaneous production of lead and tin hydrides as well as the hydrogen at that time may speed up the desorption of cadmium species from the surface of the cathode. Also the high hydrogen overvoltage and the neutral medium aided the formation and separation of cadmium hydride molecules. The generated CdH2 vapour was kinetically stable.
"The determination of trace amounts of lead in a variety of environmental samples is of great importance since lead is recognized as a cumulative poison for animals and human beings even in very minute quantities. Among the elements determined via CHG, those which easily generate stable hydrides, such as As and Se, have been the goal of several studies  , but those, the hydrides of which are difficult to generate, such as Pb, have been investigated to a lesser extent          . In most of the articles appearing in the literature, oxidation of Pb 2+ to Pb "
[Show abstract][Hide abstract] ABSTRACT: Working electrodes made out of pyrolytic graphite, glassy carbon, platinum and cadmium were compared for the electrochemical generation of volatile lead species. The same electrolytic cell, using each of the different working electrodes was coupled to an atomic absorption spectrometer and the experimental conditions were optimized in each case, using a univariate approach, to produce the maximum possible amount of volatile lead species. The experiments were focused on the variation of cathode hydrogen overvoltage by the application of a constant current during analysis. Under optimum conditions the performance of the electrochemical hydride generator cell should depend on the cathode material selected due to the different hydrogen overpotential of each material. The lead absorbance signal was taken as a measure of the efficiency of volatile lead species production. Best results were obtained using the Cd cathode, due to its relatively highest hydrogen overpotential, a carrier gas (Ar) flow rate of 55 mL min− 1 an electrolytic current of 0.8 A and a catholyte (HCl) concentration 0.05 mol L− 1. The analytical figures of merit of the method using the Cd electrode were evaluated and the susceptibility of the method to interferences was assessed by its application to the determination of trace amounts of lead in the presence of the most significant interferents. The calibration curve was linear between 0.5 and 15 μg L− 1 Pb. Detection limits and characteristic mass values were 0.21 μg L− 1 and 0.26 μg L− 1 respectively. A bovine liver standard reference material and a spiked urine sample were analyzed to check accuracy.
Spectrochimica Acta Part B Atomic Spectroscopy 05/2012; s 71–72:107–111. DOI:10.1016/j.sab.2012.03.009 · 3.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel disk electrochemical hydride generator has been developed for the determination of As and Sb. Compared with the traditional thin-layer cell, the disk cell combined the advantages of quick assembly and easy operation. This electrochemical system for hydride generation in neutral buffer solutions has been studied for analytical usefulness in coupling with atomic fluorescence spectrometry. It was found that the use of neutral phosphate buffer solution could markedly increase the fluorescence intensity of As(III) and Sb(III) and reduce the impact of cathode erosion on the stability of signal intensity. At the same time, the fluorescence intensity of As(V) and Sb(V) were almost suppressed totally. The detection limits (3 sigma) of 0.031 microgL(-1) As(III) and 0.026 microgL(-1) Sb(III) in aqueous solutions were obtained, respectively. The precisions (n=11) for 20 microgL(-1) As(III) and Sb(III) were 2.0% and 2.7%, respectively. The method was successfully applied for determination of different oxidation states of As and Sb in environmental samples.
[Show abstract][Hide abstract] ABSTRACT: An electrochemical hydride generation (ECHG) technique was developed to improve the determination of thallium by atomic spectrometry. The technique is based on the catholyte variation system for production of thallium hydride. Using Pb-Sn alloy as cathode, a transient peak shaped signal was achieved and its height, the maximum absorbance value, was taken as an analytical parameter. Parameters that might affect the hydride generation efficiency were investigated and the analytical performance of the method under the optimized experimental conditions was assessed. The linear range was 1-250 ng mL(-1) for thallium and the relative standard deviation of the method was 4.2% (RSD, n=7). The LOD for thallium was found to be 0.8 ng mL(-1), showing a significant improvement relative to conventional chemical hydride generation techniques. The proposed method was applied to the determination of thallium in unalloyed zinc standard reference material. This method offers high sensitivity, simplicity, rapidness, freeness from reagent and low acid consumption.
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